1. Field of the Invention
This invention relates to electronic flash devices and, more particularly, to a flash emission stopping circuit of an electronic flash device.
2. Description of the Prior Art
It is generally known to provide an automatic computer flash device of the series control type in which there is provided a switching element in series with the discharge tube in the discharge path of the main capacitor so that when the light measuring circuit produces a flash emission stopping signal, the charge stored on the commutating capacitor is discharged through the flash duration control switch. This applies a reverse bias to the switching element that is connected in series with the above-described discharge tube, thereby terminating the duration of the firing of the discharge tube.
In this conventional automatic computer flash device, the opening of the switching element is followed by charging of the commutating capacitor in the reverse direction through the discharge tube and, after the completion of that reversely-directed charging, the commutating capacitor is charged again in the direction reverse to that in which the first charging occurred to return to the initial state. This arrangement results in the disadvantage that this recovery time of the commutating capacitor, in returning to the initial state, amounts to as long as, for example, 0.2-0.3 (second). The reason for the large recovery time is because the capacitance of the commutating capacitor itself is large on account of its arrangement in the circuitry, and the resistor connected in the charge path of the commutating capacitor has also a very large resistance value.